First of all, Nokia is not going down anymore... But it's sales has been dramatically increasing, profits regenerated.
2ndly HTC did produce WP8 devices but they turned out to be crap that's why they decided to change OS...
I mean Htc 8x,8s,Radar...

Did you saw the Lumia 610 ? 800Mhz Arm + 256 Ram
Lumia 510 ? WP8... 800Mhz Arm + 256 Ram
Did you see how smooth these device run ?
I use android with 1Ghz single core + 512 Ram and damn it was laggy as hell !
So get your facts right before po...